This invention relates to the damping of vibration, and more particularly to the damping of vibration in rotating devices. The invention has particular application to the attenuation of screech noise from railraod wheels.
Assemblies for damping vibration in rotating devices are known. Many involve the use of relatively heavy damping assemblies, which is undesirable from the standpoint of adding an additional load to the rotating device as well as safety. In the present invention, a lightweight damping assembly is provided.
One example of prior damping techniques is illustrated by Smith, U.S. Pat. No. 2,267,311 issued Dec. 23, 1941. That patent discloses use of a vibration-dampening member which is die-stamped from a sheet of steel and has the general configuration of the wheel to which it is attached. The present invention avoids the need to die-stamp sheet metal.
Another example of a prior damping assembly is Watter, U.S. Pat. No. 2,605,132 issued July 29, 1952. In that patent, two metal rings with a thin annulus of rubber vulcanized thereto are employed as a damping assembly which is force fitted onto a wheel. The force fitting requires a cooling of the ring by packing it in dry ice, e.g., to cause the ring to shrink to a diameter permitting it to be installed on the wheel, following which the ring expands and is locked to the wheel as it returns to normal temperature. In the present invention, in contrast, vulcanizing of rubber and temperature treatment of a damping ring assembly for fitting that assembly to a wheel are not required.
The present invention involves a vibration damping assembly for a wheel or the like that includes an annular groove in a surface of the wheel and coaxial with the wheel axis. A viscoelastic damping material subject to shear deformation during rotation of the wheel is positioned within the groove against the surface of the groove, and an annular metal ring is positioned in the groove against the viscoelastic damping material, with the damping material sandwiched between the ring and wheel. Preferably the viscoelastic damping material is adhesively secured to both the wheel and the ring for enhanced damping, although it is possible to omit the adhesive if desired. It is believed that enhanced vibration damping will be achieved through the use of adhesive, such as a flexible epoxy adhesive. Also, it is preferable to position the damping assembly on the wheel so that it does not extend outwardly beyond the plane defining the edge of the wheel. In this fashion, particularly with a railroad wheel or other rotating wheel that may come in contact with external mechanisms, the damping assembly is protected and will not be subjected to external forces that might damage it.
The invention will be more completely understood by reference to the following detailed description.